This application claims priority from Korean Patent Application No. 2000-30084, filed Jun. 1, 2000, the entirety of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates in general to a method for the fabrication of a capacitor of a memory device, and more particularly to a method of fabricating a capacitor of a semiconductor device, which is capable of increasing a charge storage capacitance of the capacitor while preventing generation of leakage current in the capacitor.
2. Description of the Related Art
With recent advances in semiconductor fabrication technology, a demand for memory devices increases rapidly. In semiconductor devices, a capacitor being used as a data storage element is varied in its capacitance depending on the area of its electrodes, the distance between the electrodes, and the dielectric constant of the dielectric film interposed between the electrodes.
For these reasons, there has been generally applied a capacitor that has a TaON thin film having an excellent dielectric constant. This capacitor has a polysilicon film, as a lower electrode, that is generally treated by RTN (Rapid Thermal Nitridation) at its surface. However, with a gradual increase in the integration density of the semiconductor device, a capacitance per cell required for stable device operation remains unchanged, whereas the cell size of the capacitor is gradually decreased.
Moreover, the TaON thin film capacitor structure having, as a lower electrode, the polysilicon film of about 30 xc3x85 thickness corresponding to an effective oxide film thickness, has a limitation with respect to its capacitance. Thus, in order to maximize the capacitance of the TaON thin film capacitor, a metal film other than the polysilicon film has been formed as a lower electrode to form a capacitor structure of metal film-dielectric film-metal film (MIM).
However, if the metal film is formed as the lower electrode as described above, the metal film is then oxidized during thermal process following depositing a TaON thin film having an excellent dielectric constant on the metal film. This has a significant effect on a lifting or leakage current characteristic of the TaON thin film. Thus, in the prior art, the TaON thin film is treated by RTP (Rapid Thermal Processing) using an O2 gas at low temperature or by plasma excited in an O2 gas, to prevent oxygen deficiency in the thin film or to remove carbons present in the thin film. However, the fabricating method of the capacitor of the semiconductor device according to the prior art suffers from problems as described below.
In the fabricating method of the capacitor according to the prior art, when the deposited TaON thin film is treated by the subsequent thermal process using an O2 gas or by plasma excited in the O2 gas, the O2 gas has a slow activation speed as compared to other gases containing oxygen, so that it becomes slow in its reaction with precursors for the TaON film. Thus, the TaON thin film has oxygen deficiency and carbons present therein. This results in generation of leakage current in the TaON film, thereby deteriorating electrical properties of the capacitor.
The present invention solves prior problems and provides a fabricating method of a capacitor of a semiconductor device, which is capable of improving a leakage current characteristic of the capacitor having a TaON thin film.
Additionally, the present invention provides a fabricating method of a capacitor of a semiconductor device, which can increase a charge storage capacitance of the capacitor and thus makes the capacitor suitable for application in a highly integrated semiconductor device.
In one embodiment, the present invention provides a fabricating method of a capacitor of a semiconductor device, comprising the steps of: forming a ruthenium film as a lower electrode on a semiconductor substrate; depositing an amorphous TaON film having an excellent dielectric constant on the ruthenium film; subjecting the resulting substrate to a first thermal treatment to prevent oxidation of the lower electrode and to remove carbons present in the amorphous TaON thin film; subjecting the resulting substrate to a second thermal treatment to crystallize the amorphous TaON film; and forming an upper electrode on the crystalline TaON film.
In another embodiment, the present invention provides a fabricating method of a capacitor of a semiconductor device, comprising the steps of: forming a ruthenium film as a lower electrode on a semiconductor substrate; forming an amorphous TaON thin film having an excellent dielectric constant on the ruthenium film; subjecting the resulting substrate to a first thermal treatment using a plasma to prevent oxidation of the lower electrode and to remove carbons present in the amorphous TaON thin film; subjecting the resulting substrate to a second thermal treatment using a RTP annealing to crystallize the amorphous TaON film; and forming an upper electrode on the crystalline TaON film.